Absorbent article containing a wetlaid unitary stratified composite

ABSTRACT

A unitary stratified composite composed of a first stratum and a second stratum integrally connected by a transition zone is disclosed. The first stratum serves as a liquid acquisition stratum that rapidly acquires and then transfers liquid to the second stratum. The second stratum serves to withdraw liquid from the first stratum and further serves as a temporary storage stratum. Methods for forming the unitary stratified composite are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 09/137,503, filed Aug. 20, 1998, which is a continuation ofinternational application number PCT/US97/22342, filed Dec. 5, 1997,which is a continuation-in-part of U.S. patent application Ser. No.60/032,916, filed Dec. 6, 1996, priority of the filing dates of which ishereby claimed under 35 U.S.C. §§ 120 and 119, respectively. Each ofthese applications is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an absorbent composite and methods formaking the same and, more particularly, to a unitary stratifiedcomposite having a first stratum and a second stratum integrallyconnected by a transition zone.

BACKGROUND OF THE INVENTION

Cellulose fibers derived from wood pulp are used in a variety ofabsorbent articles, for example, diapers, incontinence products, andfeminine hygiene products. It is desirable for the absorbent articles tohave a high absorbent capacity for liquid, as well as to have good dryand wet strength characteristics for durability in use and effectivefluid management. In addition to absorbent capacity, the ability torapidly absorb a liquid is a desirable characteristic of an absorbentarticle. For example, diapers and other hygienic products that do notcontain a dedicated liquid acquisition component, suffer from liquidleakage and rewet (i.e., the feeling of dampness to touch after use).Hygienic products that contain only a high loft nonwoven acquisitionlayer suffer from a lack of fast temporary liquid storage capability andleakage. Hygienic products that contain cellulose-based acquisitionlayers suffer from rewet due to the temporary storage capability of thecellulose's fibers and lack of complete drainage. Further,cellulose-based acquisition materials have poor wet and dry integrity.

One solution to the problem of providing absorbent articles that possessthe advantageous properties of high absorbent capacity, rapid liquidacquisition, reduced leakage, and superior rewet performance has beenthe production of absorbent articles that contain multiple layers. Forexample, the combination of one layer having rapid liquid acquisitioncharacteristics with another layer having high absorbent capacityresults in a product that offers the advantages of both strata. Someimprovements in the performance of products that include multiple layershave been directed to the integration of the layers. Approaches toincreased integration typically include methods of bonding one layer tothe next. Increasing the commingling between, for example, a liquidacquisition layer and a liquid storage layer can increase fluidcommunication and the rate and drainage efficiency at which theacquisition layer releases liquid to the storage layer, therebyincreasing the product's overall liquid containment capability.

Despite the advantages associated with multiply layered absorbentproducts, problems related to the effective layer-to-layer fluidcommunication of diverse materials, and the economic costs of producing,handling, and bonding individual component layers remain.

Accordingly, there exists a need for an integrated absorbent materialthat provides the dry feel and rapid liquid acquisition of a high-loft,nonwoven material, and rapid temporary storage capability and rapidliquid acquisition performance of cellulose fibers such as crosslinkedcellulose pad. The present invention seeks to fulfill these needs andprovides further related advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a schematic view of a representative unitary stratifiedcomposite produced in accordance with the present invention;

FIG. 2 is a schematic view of one absorbent article incorporating aunitary stratified composite produced in accordance with the presentinvention;

FIG. 3 is a schematic view of another absorbent article incorporating aunitary stratified composite produced in accordance with the presentinvention;

FIG. 4 is a schematic view of another absorbent article incorporating aunitary stratified composite produced in accordance with the presentinvention;

FIG. 5 is a schematic view of still another absorbent articleincorporating a unitary stratified composite produced in accordance withthe present invention;

FIG. 6 is a schematic view of yet another absorbent articleincorporating a unitary stratified composite produced in accordance withthe present invention;

FIG. 7 is a schematic view of another absorbent article incorporating aunitary stratified composite produced in accordance with the presentinvention;

FIG. 8 is graph comparing the effect of first stratum fiber denier andpore size on the acquisition time and rewet performance of diapersincorporating representative unitary stratified composites produced inaccordance with the present invention;

FIG. 9 is graph comparing the effect of a binder system on theacquisition time and rewet performance of diapers incorporatingrepresentative unitary stratified composites produced in accordance withthe present invention;

FIG. 10 is graph comparing the effect of densification on theacquisition time and rewet performance of diapers incorporatingrepresentative unitary stratified composites produced in accordance withthe present invention;

FIG. 11 is a photomicrograph (15.0×magnification) of a portion of arepresentative unitary stratified composite produced by an air-laidmethod in accordance with the present invention;

FIG. 12 is a photomicrograph (100×magnification) of a portion of therepresentative unitary stratified composite shown in FIG. 11;

FIG. 13 is a photomicrograph (15×magnification) of a portion of arepresentative unitary stratified composite produced by a wet-laidmethod in accordance with the present invention;

FIG. 14 is a photomicrograph (100×magnification) of a portion of therepresentative unitary stratified composite shown in FIG. 13;

FIG. 15 is a photomicrograph (15×magnification) of a portion of arepresentative unitary stratified composite produced by a foam-formedmethod in accordance with the present invention;

FIG. 16 is a photomicrograph (100×magnification) of a portion of therepresentative unitary stratified composite shown in FIG. 15;

FIG. 17 is a photomicrograph (15×magnification) of a portion of arepresentative unitary stratified composite produced by a foam-formedmethod in accordance with the present invention;

FIG. 18 is a photomicrograph (100×magnification) of a portion of therepresentative unitary stratified composite shown in FIG. 17;

FIG. 19 is a photomicrograph (12×magnification) of a transition zone ofa representative unitary stratified composite produced by a foam-formedmethod in accordance with the present invention; and

FIG. 20 is a photomicrograph (40×magnification) of the transition zoneof the representative unitary stratified composite shown in FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the present invention provides an absorbent compositethat is a unitary stratified composite. The composite is stratified inthat the composite includes strata or layers, and unitary in that thestrata are integrally connected through a transition zone to provide twostrata in intimate fluid communication. Generally, the absorbentcomposite is composed of a first stratum that includes a hydrophobicfibrous material that does not absorb bodily fluids and which forms anopen and bulky stratum having a relatively low basis weight, and asecond stratum that includes a hydrophilic fibrous material, such ascrosslinked cellulose fibers, and having a basis weight preferablygreater than the first stratum. Either one or both strata can alsoinclude a binder to effect bonding between the fibers of the firststratum, between the fibers of the second stratum, and between thefibers of the top and second strata of the unitary stratified composite.The unitary stratified composite of the present invention can beincorporated into a variety of absorbent products and articles toprovide rapid temporary storage capacity, to increase the liquidacquisition rate, to reduce leakage, and to improve the rewet and dryfeel performance of the absorbent article.

In another aspect of the present invention, methods for producing aunitary stratified composite are provided. The methods of the presentinvention include wet laid, dry laid, and foam processes.

In another aspect, a preferred hygiene product converting processincorporating the unitary stratified composite of the present inventionis provided.

Referring to FIG. 1, the unitary stratified composite of the presentinvention, indicated generally by reference numeral 10, includes a firststratum 12 and a second stratum 14. The first stratum of the unitarystratified composite serves primarily as an acquisition stratum that canrapidly acquire liquid at the point of insult, and then rapidly andcompletely pass the liquid to the second stratum. The first stratum alsoserves as an antiwet back stratum having greater pore size and lowerhydrophilicity than the second stratum. The second stratum serves torapidly withdraw liquid from the first stratum and also serves as atemporary reservoir for the liquid gush associated with the release ofbodily fluids. Representative composites of the invention formed inaccordance with the present invention are shown in FIGS. 11-20. Thesubstantially homogeneous individual fibrous strata are clearly apparentin FIGS. 11, 13, 15, and 17.

The composite's transition zone, which integrally connects the first andsecond strata and provides for intimate fluid communication, includesfibers from one stratum extending into the other. The transition zonecan include hydrophobic fibers extending from the first stratum into thesecond stratum, as well as hydrophilic fibers extending from the secondstratum into the first stratum. While the first stratum may besubstantially coextensive with the second stratum, the transition zoneis substantially coextensive with at least one of the composite'sstratum. The unitary stratified composite's transition zone isillustrated in FIGS. 11-20, which show representative composites formedin accordance with the present invention. Referring to these FIGURES,the transition zone is located in the composite generally between thesubstantially homogeneous regions of the individual strata and isdefined as the region of the composite where the fibers from one stratumare commingled with fibers from the other stratum. The transition zoneis clearly illustrated in FIGS. 19 and 20, which show the commingling offibers extending from one stratum into the other for representativecomposites formed by air-laid, wet-laid, and foam-formed methods,respectively. Referring to FIGS. 19 and 20, the composite's transitionzone is characterized by the commingling of relatively smooth, tubularhydrophobic fibers (i.e., polyethylene terephthalate fibers) of thefirst stratum with the relatively kinked, ribbon-shaped hydrophilicfibers (i.e., crosslinked cellulosic fibers) of the second stratum.

The first stratum of the absorbent composite is generally a hydrophobicstratum that includes a hydrophobic fibrous material (i.e., one or morehydrophobic fibers). Other fibers, such as hydrophilic fibers, may beincluded in the first stratum as long as the overall first stratumremains relatively less hydrophilic than the second stratum. The firststratum can be composed of natural and/or synthetic fibers that do notsignificantly absorb bodily fluids, and that form an open (i.e., porous)and bulky stratum or web. The first stratum's pore size is preferablygreater than the second stratum's and allows efficient fluidcommunication and drainage to the second stratum. Suitable syntheticfibers include, for example, polyethylene terephthalate (PET),polyethylene, polypropylene, nylon, latex, rayon. The synthetic fibersare present in an amount up to about 90% by weight of the first stratum.Suitable natural fibers include, for example, cotton, wool, wood pulp,straw, kenaf, and other cellulosic fibers. In a preferred embodiment,the cellulosic fibers are crosslinked cellulosic fibers present in anamount up to about 90% by weight. The fibers noted above can optionallyinclude one or more additives, such as wet strength agents, sizingagents, and surface active agents. The fibers noted above arecommercially available from a number of suppliers including HoechstCelanese, DuPont, Eastman Chemical, Hercules, Danaklon, Inc., andWeyerhaeuser Company. In a preferred embodiment, the first stratumincludes a synthetic fiber and, more preferably, the first stratumincludes polyethylene terephthalate.

Generally, the greatest rate of liquid acquisition is attained withcomposites having relatively low density. The formation of low-densitycomposites can be achieved by varying the individual components of thecomposite. The performance of the unitary stratified composite of thepresent invention is dependent upon a number of factors including thelength, denier (g/m), crimping (crimps per inch), type of fibertreatment and physical and chemical nature of the fibers of the firststratum. Suitable fibers useful for construction of the first stratumhave a length up to about 4 inches, and preferably have a length betweenabout 0.25 and about 1.5 inches. Suitable fibers include fibers havingdenier up to about 40 denier, and preferably between about 5 and about20 denier. While straight fibers can be advantageously used in theformation of the first stratum, in a preferred embodiment, the firststratum includes from about 50% to about 100% by weight of total crimpedfibers. In a preferred embodiment, the fibers have up to about 30 crimpsper inch and more preferably from about 1 to about 20 crimps per inch.In a most preferred embodiment, the first stratum includes 100% crimpedfibers by weight of total fibers having from about 5 to about 15 crimpsper inch. Thus, in a preferred embodiment, the first stratum includespolyethylene terephthalate fibers having relatively high denier, longlength, and low crimp level.

In another preferred embodiment, the synthetic fibers include polyesterfibers having morphologies other than the conventional homogeneous solidfibers noted above. Composites of the invention comprising hollow,deep-grooved, and lobal polyester fibers exhibit advantageous liquidacquisition characteristics. For example, deep-grooved fibers providecomposites having low rewet, possibly due in part to improved capillarywicking in the grooves and more rapid liquid evaporation. Hollow fibersprovide a composite having enhanced loft compared to composites thatinclude homogeneous solid fibers. Lobal fibers (i.e., fibers havinglobal cross-sectional shape) provide composites having a greaterresistance to wet collapse compared to solid, round cross-sectionedfiber. For example, lobal polyester fibers are commercially availablefrom Hoechst Celanese.

As noted above, the first stratum includes a binder. Suitable bindersinclude, but are not limited to, cellulosic and synthetic fibrousmaterials, bonding agents, soluble bonding mediums, and wet strengthagents as described below. In one preferred embodiment, the binderincludes bicomponent binding fibers, such as Celbond® (Hoechst Celanese)and D-271P® (DuPont). In another preferred embodiment, the binderincludes a soluble binding medium, more preferably cellulose acetateused in combination with the solvent triacetin and/or triethyl citrate.For embodiments of the first stratum that include a binder, the binderis included in the stratum in an amount ranging from about 10% to about50% by weight of the components of the first stratum. Preferably, thebinder is integrally incorporated into or onto the fibrous web that isformed in the production of the unitary stratified composite. The bindercan be added to fibers prior to web formation, by applying the binder tothe air-laid, wet-laid, or foam-formed web after web deposition, afterdrying, or a combination thereof.

Generally, the first stratum of the unitary stratified composite has abasis weight of about 10 to about 100 g/m². The density of the firststratum can range from about 0.01 to about 0.3 g/cm³, and preferablyfrom about 0.01 to about 0.08 g/cm³.

The second stratum of the unitary stratified composite of the presentinvention can be a hydrophilic stratum relative to the first stratum andinclude a hydrophilic fibrous material (i.e., one or more hydrophilicfibers). The second stratum can also include other fibers, such ashydrophobic fibers (e.g., synthetic fibers such as polyester fibersincluding polyethylene terephthalate fibers), and these fibers can beincluded in the second stratum in an amount up to about 90% by weight ofthe stratum, provided that the overall stratum remains relativelyhydrophilic compared to the first stratum. The second stratum can alsoinclude mixtures of hydrophilic and synthetic fibers. Further, thesecond stratum has smaller pores than the first stratum, therebyfacilitating fluid communication between the strata and drainage fromthe first stratum. In a preferred embodiment, the hydrophilic fibersinclude cellulosic fibers in an amount up to about 90% by weight of thestratum, and more preferably crosslinked cellulosic fibers in an amountup to about 90% by weight of the stratum. In another preferredembodiment, the cellulosic fibers include chemithermomechanical pulpfibers. Suitable and preferred cellulosic fibers are described below.

Alternatively, in another embodiment, the second stratum does notinclude cellulosic fibers. In this embodiment, the stratum comprisessynthetic fibers in an amount up to about 95% by weight and binder in anamount from about 5 to about 50% by weight.

To further improve storage capacity of the absorbent composite, inanother embodiment the second stratum includes a superabsorbentpolymeric material.

In addition to hydrophilic fibers, the second stratum also includes abinder. Suitable binders for the fibers of the second stratum include,but are not limited to, those noted above and described in more detailbelow. The binder is preferably present in an amount ranging from about5% to about 50% by weight of the components of the second stratum.

The second stratum generally has a basis weight of from about 10 toabout 500 g/m². The second stratum has a density from about 0.03 toabout 0.5 g/cm³, and preferably from about 0.03 to about 0.1 g/cm³.

The second stratum is generally characterized as having a smaller poresize and increased hydrophilicity relative to the first stratum. Thus,the acquired liquid flows away from the first stratum to the morehydrophilic second stratum having smaller pores. Furthermore, becausethe pore size of the second stratum is less than the pore size of thefirst stratum, a pore size gradient is created that provides liquiddrainage away from the first stratum. See, for example, FIGS. 11-18. Theintimate commingling between the fibers of the first and second stratumof the unitary stratified composite of this invention provided by thetransition zone enables more efficient drainage of the first stratum andfluid communication between the two strata than in other absorbentproducts formed from separate and distinct acquisition and storagelayers.

The second stratum of the unitary stratified composite primarily servesto rapidly draw liquid from the first stratum. The second stratum alsoacts to temporarily store liquid acquired by the absorbent composite andprevent flow back to and beyond the first stratum. Depending upon thenature of the absorbent construct, an absorbent article incorporatingthe unitary stratified composite may include one or more additionalstrata, such as a permanent storage (see, for example, FIG. 2). In sucha construct, in addition to rapidly absorbing the acquired liquid fromthe first stratum, the second stratum has absorbent capacity sufficientto temporarily hold the acquired liquid and therefore provide timesufficient for the core stratum to permanently absorb the liquid fromthe absorbent composite.

The unitary stratified composite is produced by forming a first stratumand a second stratum, each formulated as described above. In oneembodiment, the overall absorbent composite includes a hydrophilicfibrous material (i.e., one or more hydrophilic fibers) present in theabsorbent composite in an amount from about 40% to about 90% by weightof the total composite, a hydrophobic fibrous material (i.e., one ormore hydrophobic fibers) present in the composite in an amount fromabout 1% to about 60% by weight of the total composite, and a binderpresent in the composite in an amount from about 5% to about 30% byweight of the total composite. Preferably, the hydrophilic fibers arepresent in the composite in about 60% to about 80% by weight of thetotal composite, the hydrophobic fibers are present in the composite inabout 5% to about 20% by weight of the total composite, and a binderpresent in the composite in the amount of about 10% to about 20% byweight of the total composite.

The unitary stratified composite generally has a basis weight of fromabout 20 to about 600 g/m², and preferably from about 50 to about 360g/m².

Generally, the absorbent composite has a density from about 0.01 toabout 0.4 g/cm³, and preferably from about 0.03 to about 0.15 g/cm³. Inone embodiment of the present invention, the unitary stratifiedcomposite is a densified composite. Densification methods useful inproducing the densified composites of the present invention are wellknown to those in the art. Densified unitary stratified composites ofthis invention generally have a density from about 0.1 to about 0.5g/cm³, and preferably from about 0.1 to about 0.25 g/m³.

Preferably, the unitary stratified composite of the invention is anundensified composite. Accordingly, production methods used inconnection with the absorbent composite preferably do not includesubjecting the absorbent composite, or absorbent articles thatincorporate the absorbent composite, to densification conditions. Forexample, in the production of diapers that incorporate the absorbentcomposite of the present invention, the absorbent composite ispreferably incorporated into the diaper after the diaper has beensubjected to the application of pressure such as, for example, beingpassed through a calender roll.

The unitary stratified composite can be produced in a number of formsincluding sheets, rolls, boxes, and cartridges and having a variety ofthicknesses.

As noted above, cellulosic fibers are the preferred basic component ofthe second stratum of unitary stratified composite of the presentinvention. Although available from other sources, cellulosic fibers arederived primarily from wood pulp. Suitable wood pulp fibers for use withthe invention can be obtained from well-known chemical processes such asthe Kraft and sulfite processes, whether bleached or unbleached. Thepulp fibers may also be processed by thermomechanical,chemithermomechanical methods, or combinations thereof. The preferredpulp fiber is produced by chemical methods. Ground wood fibers, recycledor secondary wood pulp fibers, and bleached and unbleached wood pulpfibers can be used. The preferred starting material is prepared fromlong fiber coniferous wood species, such as southern pine, Douglas fir,spruce, and hemlock. Details of the production of wood pulp fibers arewell-known to those skilled in the art. These fibers are commerciallyavailable from a number of companies, including Weyerhaeuser Company,the assignee of the present invention. For example, suitable cellulosefibers produced from southern pine that are usable with the presentinvention are available from Weyerhaeuser Company under the designationsCF416, NF405, NB416, PL416, and FR516.

The wood pulp fibers useful in the present invention can also bepretreated prior to use with the present invention. This pretreatmentmay include physical treatment, such as subjecting the fibers to steam,twisting or crimping and/or chemical treatment, for example,crosslinking the cellulose fibers using any of a variety of conventionalcrosslinking agents such as dimethyldihydroxyethyleneurea. Specifically,crosslinking wood pulp fibers increases their resiliency, and therebycan improve their absorbency. Crosslinked cellulose fibers and methodsfor their preparation are known in the art and are disclosed in, forexample, U.S. Pat. No. 5,225,047, issued Jul. 6, 1993, entitled“Crosslinked Cellulose Products and Method For Their Preparation,”expressly incorporated herein by reference. Suitable crosslinkedcellulose fibers produced from southern pine are available fromWeyerhaeuser Company under the designation NHB416.

Although not to be construed as a limitation, other examples ofpretreating fibers include the application of fire retardants to thefibers, or treatments with surfactants or other liquids, such as wateror solvents, which modify the surface of the fibers. See, for example,U.S. patent application Ser. No. 08/669,406, now U.S. Pat. No.5,837,627, filed Jul. 3, 1996, and entitled “Fibrous Web Having ImprovedStrength and Method of Making the Same.” Still other pretreatmentsinclude exposure to or incorporation of antimicrobials, pigments, anddensification or softening agents. Fibers pretreated with otherchemicals, such as thermoplastic and thermosetting resins, also may beused. Combinations of pretreatments also may be employed. Absorbent websmay also be similarly treated after web formation.

Any of the previously noted cellulosic fibers or pretreated cellulosicfibers treated with particle binders and/or densification/softness aidsknown in the art can also be employed in accordance with the presentinvention. The particle binders serve to attach other materials, such assuperabsorbent polymers, to the cellulosic fibers. Cellulosic fiberstreated with suitable particle binders and/or densification/softnessaids and the process for combining them with cellulose fibers aredisclosed in the following U.S. patents and patent applications: (1)U.S. Pat. No. 5,543,215, entitled “Polymeric Binders for BindingParticles to Fibers”; (2) U.S. Pat. No. 5,538,783, entitled“Non-Polymeric Organic Binders for Binding Particles to Fibers”; (3)U.S. Pat. No. 5,300,192, entitled. “Wet Laid Fiber Sheet ManufacturingWith Reactivatable Binders for Binding Particles to Binders;” (4) U.S.Pat. No. 5,352,480, entitled “Method for Binding Particle to FibersUsing Reactivatable Binders”; (5) U.S. Pat. No. 5,308,896, entitled“Particle Binders for High-Bulk Fibers”; (6) Ser. No. 07/931,279, nowU.S. Pat. No. 5,589,256, filed Aug. 17, 1992, entitled “Particle Bindersthat Enhance Fiber Densification”; (7) Ser. No. 08/107,469, now U.S.Pat. No. 5,672,418, filed Aug. 17, 1993, entitled “Particle Binders”;(8) Ser. No. 08/108,219, now U.S. Pat. No. 5,607,759, filed Aug. 17,1993, entitled “Particle Binding to Fibers”; (9) Ser. No. 08/107,467,now U.S. Pat. No. 5,693,411, filed Aug. 17, 1993, entitled “Binders forBinding Water Soluble Particles to Fibers”; (10) U.S. Pat. No.5,547,745, entitled “Particle Binders”; (11) Ser. No. 08/108,218, nowU.S. Pat. No. 5,641,561, filed Aug. 17, 1993, entitled “Particle Bindingto Fibers”; and (12) U.S. Pat. No. 5,308,896, entitled “Particle Bindersfor High-Bulk Fibers,” all expressly incorporated herein by reference.One example of a suitable densification/softness aid is a mixture of 70%sorbitol and 30% glycerin. The absorbent is treated with sorbitol andglycerin by spraying the absorbent with the mixture or passing theabsorbent through a curtain coater, or other means familiar to thoseskilled in the art of adding a liquid to an absorbent sheet.

Materials that enhance absorbent capacity, such as superabsorbentpolymers, can also be combined with the unitary stratified composite ofthe present invention. A superabsorbent polymer as used herein is apolymeric material that is capable of absorbing large quantities offluid by swelling and forming a hydrated gel (hydrogel). Thesuperabsorbent polymers also can retain significant amounts of waterunder moderate pressures. Superabsorbent polymers generally fall intothree classes, namely, starch graft copolymers, crosslinkedcarboxymethylcellulose derivatives and modified hydrophilicpolyacrylates. Examples of such absorbent polymers are hydrolyzedstarch-acrylonitrile graft copolymer, a neutralized starch-acrylic acidgraft copolymer, a saponified acrylic acid ester-vinyl acetatecopolymer, a hydrolyzed acrylonitrile copolymer or acrylamide copolymer,a modified crosslinked polyvinyl alcohol, a neutralizedself-crosslinking polyacrylic acid, a crosslinked polyacrylate salt,carboxylated cellulose, and a neutralized crosslinked isobutylene-maleicanhydride copolymer. The superabsorbent polymers can be combined withthe cellulosic fibers in amounts up to 70% by weight based on the totalweight of fibers and polymer.

Superabsorbent polymers are available commercially, for example, starchgraft polyacrylate hydrogel fines from Hoechst Celanese of Portsmouth,Va. These superabsorbent polymers come in a variety of sizes,morphologies, and absorbent properties. These are available from HoechstCelanese under trade designations such as IM 1000 and IM 3500. Othersuperabsorbent particles are marketed under the trademarks SANWET(supplied by Sanyo Kasei Kogyo Kabushiki Kaisha), SUMIKA GEL (suppliedby Sumitomo Kagaku Kabushiki Kaisha), which is suspension polymerizedand spherical, as opposed to solution polymerized ground particles,FAVOR (supplied by Stockhausen of Greensboro, N.C.), and NORSOCRYL(supplied by Atochem). Other superabsorbent polymers are described inU.S. Pat. Nos. 4,160,059; 4,676,784; 4,673,402; 5,002,814; 5,057,166;4,102,340; and 4,818,598, expressly incorporated herein by reference.Products such as diapers that incorporate superabsorbent polymers areshown in U.S. Pat. Nos. 3,669,103 and 3,670,731.

Increased wet and dry strength of the unitary stratified composite ofthe present invention can be accomplished with a binder. As used herein,the term “binder” refers to a system that is effective in mechanicallyintertwining or bonding the materials within the first stratum, thematerials within the second stratum, and the first stratum to the secondstratum. In one embodiment of the present invention, both strata includea binder. In another embodiment, only the second stratum includes abinder, and in still another embodiment, only the first stratum includesa binder. Suitable binders can include, but are not limited to, bondingagents such as thermoplastic and thermosetting materials, solublebonding mediums used in combination with solvents, and wet strengthagents. Alternatively, integral commingling and intimate contact betweenthe composite's strata can be achieved through mechanical processesincluding, for example, hydroentanglement, embossing, tenderizing, andneedling processes, among others.

Bonding agents useful in the binder in accordance with the presentinvention are those materials that (a) are capable of being combinedwith and dispersed throughout a web of fibers, (b) when activated, arecapable of coating or otherwise adhering to the fibers or forming abinding matrix, and (c) when deactivated, are capable of binding atleast some of the fibers together. The use of bonding agents withcellulose fiber webs is disclosed in U.S. patent application Ser. No.08/337,642, filed Nov. 10, 1994, entitled “Densified Cellulose FiberPads and Methods of Making the Same,” expressly incorporated herein byreference.

Suitable bonding agents include thermoplastic materials that areactivated by melting at temperatures above room temperature. When thesematerials are melted, they will coat at least portions of the cellulosefibers with which they are combined. When the thermoplastic bondingagents are deactivated by cooling to a temperature below their meltpoint, and preferably no lower than room temperature, the bonding agentwill, upon solidifying from the melted state, cause the cellulose fibersto be bound in a matrix.

Thermoplastic materials are the preferred binders, and can be combinedwith the fibers in the form of particles, emulsions, or as fibers.Suitable fibers can include those made from thermoplastic polymers,cellulosic or other fibers coated with thermoplastic polymers, andmulticomponent fibers in which at least one of the components of thefiber comprises a thermoplastic polymer. Single and multicomponentfibers are manufactured from polyester, polyethylene, polypropylene, andother conventional thermoplastic fiber materials. The samethermoplastics can be used in particulate or emulsion form. Manysingle-component fibers are readily commercially available. Suitablemulticomponent fibers include Celbond® fibers available from HoechstCelanese Company. A preferred crimped polymer-based binder fiber isHoechst Celanese Copolyolefin Bicomponent fiber, commercially availableunder the tradename CELBOND® from Hoechst Celanese Corporation, type255, lot 33865A, having a detex of about 3.3, a denier of about 3.0, anda fiber length of about 6.4 mm. Suitable coated fibers can includecellulose fibers coated with latex or other thermoplastics, as disclosedin U.S. Pat. No. 5,230,959, issued Jul. 27, 1993, to Young et al., andU.S. Pat. No. 5,064,689, issued Nov. 12, 1991, to Young et al. Thethermoplastic fibers are preferably combined with the cellulose fibersbefore or during the forming process. When used in particulate oremulsion form, the thermoplastics can be combined with the cellulosefibers before, during, or after the forming process.

Other suitable thermoplastic bonding agents include ethylene vinylalcohol, polyvinyl acetate, acrylics, polyvinyl acetate acrylate,polyvinyl dichloride, ethylene vinyl acetate, ethylene vinyl chloride,polyvinyl chloride, styrene, styrene acrylate, styrene butadiene,styrene acrylonitrile, butadiene acrylonitrile, acrylonitrile butadienestyrene, ethylene acrylic acid, urethanes, polycarbonate, polyphenyleneoxide, and polyimides.

Thermosetting materials also serve as excellent bonding agents for thepresent invention. Typical thermosetting materials are activated byheating to elevated temperatures at which crosslinking occurs.Alternatively, a resin can be activated by combining it with a suitablecrosslinking catalyst before or after it has been applied to thecellulosic fiber. Thermosetting resins can be deactivated by allowingthe crosslinking process to run to completion or by cooling to roomtemperature, at which point crosslinking ceases. When crosslinked, it isbelieved that the thermosetting materials form a matrix to bond thecellulose fibers. It is contemplated that other types of bonding agentscan also be employed, for example, those that are activated by contactwith steam, moisture, microwave energy, and other conventional means ofactivation.

Thermosetting bonding agents suitable for the present invention includephenolic resins, polyvinyl acetates, urea formaldehyde, melamineformaldehyde, and acrylics. Other thermosetting bonding agents includeepoxy, phenolic, bismaleimide, polyimide, melamine formaldehyde,polyester, urethanes, and urea.

These bonding agents are normally combined with the fibers in the formof an aqueous emulsion. They can be combined with the fibers during thelaying process. Alternatively, they can be sprayed onto a loose webafter it has been formed.

As noted above, the binder utilized in accordance with the presentinvention can also be a soluble bonding medium that can be incorporatedwith the pulped cellulosic fibers, either in fiber form, or as particlesor granules. If desired, the bonding medium can also be coated ontosolvent-insoluble fibers, such as cellulosic fibers, which can then bedistributed throughout the matrix of fibers making up each of the strataof the present invention. It is presently preferred that the bondingmedium comprise a fiber and be mixed with the components of each stratumprior to the formation of the absorbent. The use of soluble bondingmediums with cellulose fiber webs is disclosed in U. S. patentapplication Ser. No. 08/669,406, now U.S. Pat. No. 5,837,627, filed Jul.3, 1996, entitled “Fibrous Web Having Improved Strength and Method ofMaking the Same,” expressly incorporated herein by reference.

The solvents employed in accordance with the present invention must ofcourse be capable of partially solubilizing the bonding medium asdescribed above. The solvents must be able to partially dissipate ormigrate from the surface of the bonding medium to allow the bondingmedium to resolidify after partial solubilization. Nonvolatile solventsmay be dissipated in most part by absorption into the bonding medium. Itis preferred that the solvent be of limited volatility, so that littleor no solvent will be lost to the atmosphere. By limited volatility itis meant that the solvent has a vapor pressure of 29 kPa or less at 25°C. Using a solvent of limited volatility may mitigate precautionsusually necessary to control volatiles, and reduces the amount ofsolvent required to partially solubilize the bonding medium. Inaddition, use of solvents of limited volatility may eliminate theattendant processing problems encountered with volatile solvents, manyof which are flammable and must be handled with care. The use ofsolvents of limited volatility may also reduce environmental problems.Furthermore, it is desirable for solvents to be nontoxic and capable ofbeing dissipated from the surface of the bonding medium withoutadversely affecting the overall strength of the bonding medium.

Preferred bonding mediums and solvents of limited volatility are listedin the table set forth below.

Bonding Medium Solvent cellulose acetate triacetin propane dioldiacetate propane diol dipropionate propane diol dibutyrate triethylcitrate dimethyl phthalate dibutyl phthalate cellulose nitrate triacetincellulose butyrate triacetin vinyl chloride/vinyl acetate copolymertriacetin cellulose fibers coated with polyvinyl acetate triacetin

Of the several bonding mediums listed, cellulose acetate is the mostpreferred. During manufacture of cellulose acetate fibers, a finish isusually applied to the fibers. Many times this finish is in the form ofan oil. The presence of the finish sometimes detracts from theperformance of a bonding medium. The presence of a finish may adverselyaffect the development as well as the strength of the bonds. It has beenfound that, when the bonding fibers are as straight as possible, asopposed to curled or kinked, they provide more contact points with thecellulosic fibers, and thus the final web will develop better strength.Similarly, when the bonding fibers are as long as is reasonablypossible, the strength of the final web is increased. In addition to theforegoing, cellulose ethers and other cellulose esters may also be usedas bonding medium. Acetylated pulp fibers may also be used as bondingmedium and may be substituted with any number of acetyl groups. Apreferred degree of substitution (D.S.) would be 2 to 3, and a mostpreferred D.S. would be 2.4.

The solvents used in combination with the bonding medium can be added invarying amounts. Strength is adversely affected if too little or toomuch solvent is added. At a cellulose acetate/pulp weight ratio of10:90, it has been found that the solvents, and particularly triacetin,provide good strength when added in amounts ranging from 6% to 17%, andmost preferably in the range of 9% to 14%, based on the weight of pulpfiber present.

The preferred forms of the solvents propane diol diacetate,dipropionate, and dibutyrate are the 1, 2 and 1, 3 forms. Other suitablesolvents that work in accordance with present invention are butylphthalyl butyl glycolate, N-cyclohexyl-p-toluenesulfonamide, diamylphthalate, dibutyl phthalate, dibutyl succinate, dibutyl tartrate,diethylene glycol dipropionate, di-(2-ethoxyethyl) adipate,di-(2-ethoxyethyl) phthalate, diethyl adipate, diethyl phthalate,diethyl succinate, diethyl tartrate, di(2-methoxyethyl) adipate,di-(2-methoxyethyl) phthalate, dimethyl phthalate, dipropyl phthalate,ethyl o-benzoylbenzoate, ethyl phthalyl ethyl glycolate, ethylene glycoldiacetate, ethylene glycol dibutyrate, ethylene glycol dipropionate,methyl o-benzoylbenzoate, methyl phthalyl ethyl glycolate, N-o andp-tolylethylsulfonarnide, o-tolyl p-toluenesulfonate, tributyl citrate,tributyl phosphate, tributyrin, triethylene glycol diacetate,triethylene glycol dibutyrate, triethylene glycol dipropionate, andtripropionin.

The binder useful in the absorbent composite of the invention can alsoinclude polymeric agents that can coat or impregnate cellulosic fibers.Suitable such agents include cationic modified starch havingnitrogen-containing groups (e.g., amino groups) such as those availablefrom National Starch and Chemical Corp., Bridgewater, N.J.; latex; wetstrength agents such as polyamide-epichlorohydrin resin (e.g., Kymene™557H, Hercules, Inc., Wilmington, Del.), polyacrylamide resin(described, for example, in U.S. Pat. No. 3,556,932 issued Jan. 19, 1971to Coscia et al.; also, for example, the commercially availablepolyacrylamide marketed by American Cyanamid Co., Stanford, Conn., underthe trade name Parez™ 631 NC); urea formaldehyde and melamineformaldehyde resins, and polyethylenimine resins. A general discussionon wet strength agents utilized in the paper field, and generallyapplicable in the present invention, can be found in TAPPI monographseries No. 29, “Wet Strength in Paper and Paperboard”, TechnicalAssociation of the Pulp and Paper Industry (New York, 1965). Otherbinders could also include the use of scrim and/or continuous fiberfilaments. For embodiments of the unitary stratified composite thatinclude a wet strength agent as a binder, the wet strength agent ispresent in the composite in an amount from about 0.1% to about 2.0%,preferably from about 0.5% to about 1.0%, by weight of the totalcomposite.

Additives can also be incorporated into a unitary stratified compositeformed in accordance with the present invention during absorbentformation. The advantage of incorporating the additives during theabsorbent formation is that they will also be attached to the absorbentmatrix by certain of the solvents and bound in the matrix by the bondingmedium. This provides a significant advantage in that the additives canbe dispersed and retained throughout the matrix where desired. Forexample, the additives may be evenly dispersed and retained throughoutthe matrix. Additives that can be incorporated into the matrix includeabsorbent capacity enhancing materials such as superabsorbent polymers,adsorbents such as clays, zeolites, and activated carbon, brightenerssuch as titanium oxide, and odor absorbents such as sodium bicarbonate.Solvents can also reduce the dusting caused by the additives or the pulpitself because more of the fines are attached and bound to the matrix bythe bonding medium.

In another aspect, the present invention provides methods for producinga unitary stratified composite. Generally, the unitary stratifiedcomposite is formed by forming a first stratum (as described above) on asecond stratum (as described above), or the reverse. Intimate connectionof the first stratum to the second stratum, and the formation of thetransition zone, occurs when the two strata are laid down as describedbelow. The unitary stratified composite of the present invention may beformed by an air-laid process, a wet-laid process, or a foam-formedprocess. A unitary stratified composite can be produced in accordancewith the present invention in a variety of methods including, forexample, air-laid or wet-laid web forming techniques known to those ofordinary skill in the pulp processing art. Representative examples ofair-laid and wet-laid processes are disclosed in U.S. patentapplications: Ser. No. 08/337,642, filed Nov. 10, 1994, entitled“Densified Cellulose Fiber Pads and Methods of Making the Same,” andSer. No. 08/669,406, now U.S. Pat. No. 5,837,627, filed Jul. 3, 1996,entitled “Fibrous Web Having Improved Strength and Method of Making theSame,” both expressly incorporated herein by reference. The absorbentcan also be produced by foam processes known in the art. See, forexample, U.S. Pat. Nos. 3,716,449; 3,839,142; 3,871,952; 3,937,273;3,938,782; 3,947,315; 4,166,090; 4,257,754; and 5,215,627, assigned toWiggins Teape and related to the formation of fibrous materials fromfoamed aqueous fiber suspensions, expressly incorporated herein byreference. Generally, the methods for forming the unitary stratifiedcomposite of this invention include the sequential or simultaneouslaying down of a first stratum (e.g., the components of the secondstratum) followed by the laying down of a second stratum (e.g., thecomponents of the first stratum) on the first laid stratum. The stratacan also be laid in reverse order. The formed strata arethen subjectedto conditions sufficient to effect bonding (i.e., air drying andheating) between and within the strata to provide the unitary stratifiedcomposite of the invention. The processed web can be delivered in rollform, spooled form, or otherwise. Preferably, the method includesfestooning as a finishing step.

Generally, the method for forming the unitary stratified compositeincludes combining the components of the first stratum, hydrophobicfibers and binder; combining the components of the second stratum,hydrophilic fibers and binder; and depositing the respective fibrousmixtures onto a foraminous support (e.g., a forming wire), eithersimultaneously or sequentially, such that intimate commingling betweenthe fibers of the strata is achieved and the transition zone is formed.The combined deposited strata are then subjected to conditionssufficient to effect interfiber bonding (e.g., heating to effect thermalbonding) to provide the unitary stratified composite of this invention.

For wet-laid and foam methods, the fiber/binder mixtures are aqueous orfoam fibrous slurries. In these methods, the deposited slurries form awater- or foam-containing composite. Accordingly, these methods furtherinclude the step of removing at least a portion of water or foam fromthe wet composite on the foraminous support. The resulting wetstratified composite is then subjected to conditions, for example,heating, to effect drying and thermal bonding of the fibers andformation of the unitary stratified composite. For foam processes, theaqueous or foam slurry further includes a surfactant.

In the composite forming methods, intimate strata commingling andtransition zone formation result from the deposition of the componentsfrom one strata onto the components of the other. The deposition processinvolves the laying down of fibrous streams, which correspond to thefirst and second strata, onto a foraminous support. Turbulenceaccompanies the deposition of the streams and mixing of the streams'components occurs. The mixing of components ultimately results in theformation of the composite's transition zone. For wet-laid and foamprocesses, the turbulence and fibrous component mixing is enhancedthrough the application of vacuum to the foraminous support, whichserves to remove water from the deposited aqueous or foam fibrousslurries. The application of vacuum to the deposited strata during thedrying process further increases the commingling of the strata andenhances the transition zone.

The fibrous slurries can be deposited onto the foraminous supportthrough the use of a divided headbox, for example, a twin slice headbox,which deposits the slurries onto the support. Mixing of the two fibrousslurries is greatest when the components of the individual strata aredeposited simultaneously. Alternatively, the fibrous slurries can bedeposited onto the support sequentially through the use of offsetheadboxes. For methods that use offset headboxes, some settling of thecomponents of the first laid stratum deposited on the support occursprior to the deposition of the components of the second stratum.

Preferably, the unitary stratified composite of the present invention isprepared by a wet-laid or foam-formed process. For fabrication, theunitary stratified composite is preferably formed by a foam process,preferably a process by Ahlstrom Company (Helsinki, Finland). Thisprocess encompasses desirable manufacturing efficiencies while producinga product with desirable performance characteristics. The formation of arepresentative unitary stratified composite of the present invention byrepresentative wet laid, air laid, foam, and commercial processes aredescribed in Examples 1 through 4, respectively. The performancecharacteristics of representative unitary stratified composites producedby the methods noted above are described in Examples 6 through 8.

As noted above, the unitary stratified composite 10 of the presentinvention includes a first stratum 12 and a second stratum 14 asschematically depicted in FIG. 1. The absorbent composite can beincorporated in an absorbent article as the absorbent stratum. Theabsorbent composite can be used alone or, as illustrated in FIG. 2, canbe used in combination with one or more secondary strata. In FIG. 2, theabsorbent composite is employed as an upper acquisition/distributionstratum in combination with a storage stratum 20 composed of, forexample, a fibrous web. Storage stratum 20, if desired, can alsocomprise a densified stratum of bonded cellulose fibers. As illustratedin FIG. 3, a third stratum 30 (e.g., a core or retention stratum) canalso be employed, if desired, with a storage stratum 20 and absorbent10. If desired, the retention stratum 30 can also be composed of afibrous web such as, for example, densified bonded cellulose fibers.Alternatively, a distribution stratum 40 can be interposed betweenabsorbent 10 and storage stratum 20 as illustrated in FIG. 4.Distribution stratum 40 is generally a hydrophilic fibrous material thatincludes, for example, hydrophilic fibers such as cellulosic fibers,preferably crosslinked cellulosic fibers, and a binder. In one preferredembodiment, the cellulosic fibers are crosslinked eucalyptus fibers.Distribution stratum 40 can optionally include superabsorbent polymericmaterial.

A variety of suitable constructs can be produced from the unitarystratified composite. The most common include absorptive consumerproducts such as diapers, feminine hygiene products such as femininenapkins, and adult incontinence products. For example, referring to FIG.5, an absorbent article 50 comprises absorbent composite 10 and anunderlying storage stratum 20. A liquid pervious facing sheet 16overlies absorbent composite 10 and a liquid impervious backing sheet 18underlies the storage stratum 20. The unitary stratified composite willprovide advantageous liquid acquisition performance for use in, forexample, diapers. The capillary structure of the absorbent compositewill aid in fluid transport in multiple wettings. Generally, the storagestratum 20 includes a fibrous web, for example, a strengthened web ofcellulose fibers, and may also incorporate additives, such assuperabsorbent polymers to significantly increase the absorbent capacityof the storage stratum 20.

The article of FIG. 5 can be assembled so that absorbent composite 10 isbrought into contact with the storage stratum 20 while the binder in thelatter is still active. Such a procedure will allow the storage stratumto bond to at least the lower surface of absorbent 10, and thuseliminate the need to use hot-melt glues to bond adjacent strata.

A stronger bond between absorbent composite 10 and the storage stratum20 can be achieved by contacting the absorbent composite with thestorage stratum while the absorbent composite's binder is still active.Similarly, laying the storage stratum 20 on the backing sheet 18 whilethe binder of the storage stratum is still active results in the bondingof stratum 20 to the backing sheet 18. In a similar manner, absorbentcomposite 10 may be bonded to the facing sheet 16 by laying the facingsheet on absorbent composite 10 while the binder therein is stillactive. Interbonding between strata can enhance and further facilitatefluid transport across the stratum interface.

The construct in FIG. 5 is shown for purposes of exemplifying a typicalabsorbent article, such as a diaper or feminine napkin. One of ordinaryskill will be able to make a variety of different absorbent constructsusing the concepts taught herein. For example, a typical constructionfor an adult incontinence absorbent structure is shown in FIG. 6. Thearticle 60 comprises a facing sheet 16, absorbent composite 10, astorage stratum 20, and a backing sheet 18. The facing sheet 16 ispervious to liquid while the backing sheet 18 is impervious to liquid.In this construct, a liquid pervious tissue 22 composed of a polar,fibrous material is positioned between absorbent composite 10 andstorage stratum 20.

Referring to FIG. 7, another absorbent article 70 includes a backingsheet 18, a storage stratum 20, an intermediate stratum 24, an absorbentcomposite 10, and a facing sheet 16. The intermediate stratum 24contains, for example, a densified fibrous material such as acombination of cellulose acetate and triacetin, which are combined justprior to forming the article. The intermediate stratum 24 can thus bondto both the absorbent composite 10 and the storage stratum 20 to form anabsorbent article with much more integrity than one in which theabsorbent composite and storage stratum are not bonded to each other.The hydrophilicity of stratum 24 can be adjusted in such a way as tocreate a hydrophilicity gradient among strata 10, 24, and 20. It shouldbe understood that an independent intermediate stratum is not requiredin order to get stratum-to-stratum bonding. When one of two adjacentstrata or both strata contain a binder, if the two strata are broughttogether when the bonding medium is still active, bonding between thetwo strata will occur and provide a stronger composite compared to acomposite lacking any bonding. Alternatively, intermediate stratum 24can be a distribution stratum as described above in reference to theconstruct of FIG. 4.

The unitary stratified composite of the present invention improves thesurface dryness rewet performance, and acquisition rate of absorbentproducts and articles that incorporate the absorbent composite. Theabsorbent composite also provides increased pad integrity, improvedappearance, and a reduction in wet collapse during use for absorbentproducts that incorporate the absorbent composite. Furthermore, becausethe unitary stratified composite can be manufactured and delivered inweb form, absorbent product manufacturing processes that include theabsorbent composite are simplified relative to manufacturing processesthat involve the handling of bales of crosslinked fibers or fluff pulp.Thus, in addition to the increased performance provided to absorbentproducts that incorporate the absorbent composite of this invention, theabsorbent composite offers economic advantages over the combination ofseparate strata of high-loft nonwoven fibers and cross-linked cellulose.

EXAMPLES

The following examples are provided for the purposes of illustration,and not limitation.

Example 1 Unitary Stratified Composite Formation: Wet Laid Method

This example illustrates a wet laid method for forming a representativeunitary stratified composite of the present invention. In this example,the absorbent composite has a first stratum composed of 90% polyethyleneterephthalate (fiber length 0.5 inches, 15 denier, crimped) (HoechstCelanese Co.) and 10% Celbond® T-105 (Hoechst Celanese Co.), and asecond stratum composed of a 90% crosslinked cellulose fiber(Weyerhaeuser Co.) and 10% Celbond® T-105.

Fiber Preparation

A lab size Waring blender was filled with 4 L of water and Celbond®T-105 (for the first stratum) was added. The mixture was blended for ashort time to “open” the synthetic fibers. The polyethyleneterephthalate (PET) fibers were then added to the Celbond® T-105/watermixture and blended for at least one minute to “open” the PET fibers andto effect mixing of the two synthetic fibers. The resulting aqueousmixture of fibers contained approximately 0.02 to 0.5% solids. Aftermixing, the aqueous fiber mixture was transferred to a secondarycontainer.

A lab size Waring blender was filled with 4 L of water and Celbond®T-105 (for the second stratum) was added. The mixture was blended for ashort time to “open” the synthetic fibers. The crosslinked cellulosefibers were then added to the Celbond® T-105/water mixture and blendedfor at least one minute to “open” the crosslinked cellulose fibers andto effect mixing of the two fibers. The resulting aqueous mixture offibers contained approximately 0.07 to 1.0% solids. After mixing, theaqueous fiber mixture was transferred to a secondary container.

Sheet Formation

A sheet was prepared using a stratified sheet mold. To the mold filledwith water was added the crosslinked cellulose fiber-Celbond® T-105mixture prepared as described above. After thorough mixing in the mold,the mold was drained down to its baffles. The mold baffles were thenclosed, and the mold refilled with water. The baffles were reopened, andthe mold drained again half way. The baffles were then closed and themold refilled with water. A portion of the PET-Celbond® T-105 mixtureprepared as described above was added to the top half of the mold. Thecontents of the top half of the mold were mixed, and then the mold wasdrained to the baffles. The baffles were then closed, and the top halfof the mold refilled with water. Another portion of the PET-Celbond®T-105 mixture was then added to the mold and mixed. The baffles wereagain opened to drain the top half of the mold, refilled with water, andanother portion of the PET-Celbond® T-105 mixture added with mixing.This procedure was repeated until all of the prepared PET-Celbond® T-105mixture was added to the mold. Upon completion of the addition, the moldwas finally drained and the resulting wet sheet carefully removed.

The representative unitary stratified composite was produced by placingthe wet sheet in a through air dryer to dry and to effect bonding.

Example 2 Unitary Stratified Composite Formation: Air Laid Method

This example illustrates an air laid method for forming a representativeunitary stratified composite of the present invention. In this example,the absorbent composite has a first stratum composed of 90% polyethyleneterephthalate (fiber length 0.5 inches, 15 denier, crimped) (HoechstCelanese) and 10% Celbond® T-105 (Hoechst Celanese), and a secondstratum composed of a 90% crosslinked cellulose fiber (Weyerhaeuser Co.)and 10% Celbond® T-105.

Fiber Preparation

PET fibers and Celbond® T-105 for the first stratum were placed in aplastic bag and thoroughly mixed with an airstream. Crosslinkedcellulose fibers and Celbond+ T-105 for the bottom stratum were placedin a second plastic bag and mixed thoroughly with an airstream.

Sheet Formation

A pinmill was used to “open” the fibers. The resulting fibers were thenevenly distributed on a tissue by first slowly metering the crosslinkedcellulose fiber-Celbond® T-105 mixture into the air former, followed byslowly metering the PET fibers-Celbond® T-105 mixture into the airformer on top of the stratum containing the crosslinked fibers.

The representative unitary stratified composite was produced by placingthe resulting air sheet in a through air dryer to effect bonding.

Example 3 Unitary Stratified Composite Formation: Laboratory Foam Method

This example illustrates a laboratory foam method for forming arepresentative unitary stratified composite of the present invention.The absorbent composite has a first stratum composed of 90% polyethyleneterephthalate (fiber length 0.5 inches, 15 denier, crimped) (HoechstCelanese) and 10% Celbond® T-105 (Hoechst Celanese), and a secondstratum composed of a 90% crosslinked cellulose fiber (Weyerhaeuser Co.)and 10% Celbond® T-105.

Fiber Preparation

The fibers were prepared as for the wet laid process described above inExample 1. The crosslinked cellulose fiber-Celbond® T-105 mixture wasplaced in a container and water added to form an aqueous mixture. Theresulting mixture was then blended for a few seconds with anair-entrapping blade. A surfactant (Incronan 30, Croda, Inc.) was addedto the blended mixture. Approximately 1 g active surfactant solids pergram fiber were added. The mixture was blended while slowly raising themixer blade height with the rising foam. After about one minute, themixing was terminated, and then restarted for another minute at constantmixer blade height. The resulting foam-fiber mixture has a volume ofabout three times the volume of the original water-fiber mixture.

A foam-fiber mixture was also prepared from the PET fiber-Celbond® T-105mixture as described above for the crosslinked cellulose fiber-Celbond®T-105 mixture.

Sheet Formation

The crosslinked cellulose fiber-Celbond® T-105 foam-fiber mixture wasrapidly poured into a sheet mold having an inclined diffusion plate.After the addition of the foam-fiber mixture, the plate was removed fromthe mold, and a strong vacuum was applied to reduce the foam-fiberheight. The vacuum was discontinued and the diffusion plate replaced.The PET fiber-Celbond® T-105 foam-fiber mixture was then added to thesheet mold. The plate was removed and a strong vacuum was again appliedto the mold. After the disappearance of most of the visible foam, theresulting sheet was removed from the mold and passed, along with aforming wire, over a slit couch to remove excess foam and water.

The representative unitary stratified composite was produced by placingthe resulting damp sheet in a through air dryer to dry and to effectbonding.

Example 4 Unitary Stratified Composite Formation: Commercial Foam Method

This example illustrates a commercial foam method for forming arepresentative unitary stratified composite of the present invention. Inthis example, the absorbent composite has a first stratum composed of90% polyethylene terephthalate (fiber length 0.5 inches, 15 denier,crimped) (Hoechst Celanese) and 10% Celbond® T-105 (Hoechst Celanese),and a second stratum composed of a 90% crosslinked cellulose fiber(Weyerhaeuser Co.) and 10% Celbond® T-105.

Fiber Preparation

Foam-fiber mixtures were prepared by combining dry fibers withsurfactant and mixing for approximately 2 minutes with an air-entrappingblade. The crosslinked cellulose fiber-Celbond® fiber mixture wasdistributed into two tanks, and the PET-Celbond® fiber mixture wasplaced in a single tank.

Sheet Formation

Using transfer pumps, the foamy fiber slurries prepared as describedabove were pumped to an inclined multilayer headbox where thecrosslinked cellulose fiber-Celbond® fiber mixture was first laid downfollowed by laying down of the PET-Celbond® fiber mixture. The wire waspassed over two-slit couch vacuum.

The representative unitary stratified composite was produced by placingthe resulting damp sheet in a through air dryer to dry and to effectbonding.

Example 5 Method for the Evaluation of Acquisition Time and Rewet forRepresentative Unitary Stratified Composites

The performance characteristics of representative unitary stratifiedcomposites of the present invention were evaluated by incorporating theabsorbent composite into a commercially available diaper and comparingthe acquisition time and rewet relative to a control diaper. Theacquisition time and rewet were determined in accordance with themultiple-dose rewet test described below.

Briefly, the multiple-dose rewet test measures the amount of syntheticurine released from an absorbent structure after each of three liquidapplications, and the time required for each of the three liquid dosesto wick into the product.

A preweighed sample of the absorbent structure is prepared for the testby determining the center of the structure's core, measuring 1 inch tothe front for liquid application location, and marking with “X,” andthen placing a liquid application funnel (minimum 100 mL capacity, 5-7mL/s flow rate) 4 inches above the surface of the sample. Commerciallyavailable diapers are used as controls, and these diapers incorporatingthe absorbent composite of the present invention were used for thecomparative evaluation. Diapers incorporating the absorbent compositewere prepared by cutting and inserting the absorbent composite into thediapers.

Once the sample was prepared, the test was conducted as follows. Flattenthe sample, nonwoven side up, onto tabletop under the liquid applicationfunnel. Fill funnel with dose (100 mL) of synthetic urine. Place dosingring ({fraction (5/32)} inch stainless steel, 2 inch ID×3 inch height)onto the “X” measured on the samples. Apply first dose of syntheticurine within the dosing ring. Using a stopwatch, record the liquidacquisition time in seconds from the time the funnel valve is openeduntil the liquid wicks into the product from the bottom of the dosingring. Wait twenty minutes. During the 20-minute waiting period after thefirst dose is applied, weigh a stack of filter papers (19-22 g, Whatman#3, 11.0 cm or equivalent, preexposed to room humidity for minimum of 2hours before testing). During the second dose waiting period, take anydry filter papers left from first dose and add additional dry papers tototal 29-32 g. During the third dose waiting period, take any dry papersand add additional dry papers to total 39-42 g. Place the stack ofpreweighed filter papers (i.e., dry blotter weight in Tables 1-9 below)on center of the wetted area and place cylindrical weight (8.9 cmdiameter, 9.8 lb.) on top of these papers. Wait two minutes. Removeweight and weigh the papers. Record the weight change. Repeat theprocedure two more times (i.e., for the second and third doses).

Rewet is reported as the amount of liquid absorbed back into the filterpapers after each liquid dose (i.e., weight of wet filter papers—weightof dry filter papers).

Liquid acquisition time is reported as the length of time (seconds)necessary for the liquid to be absorbed into the product for each of thethree doses.

The aqueous solution used in the tests is a synthetic urine availablefrom National Scientific under the trade name RICCA. The synthetic urineis a saline solution containing 135 meq./l sodium, 8.6 meq./l calcium,7.7 meq./l magnesium, 1.94% urea by weight (based on total weight), plusother ingredients.

Multiple-dose rewet test results for control diapers and diapersincorporating representative unitary stratified composites of thepresent invention are described in Examples 6 through 8.

Example 6 Evaluation of Acquisition Time and Rewet for RepresentativeUnitary Stratified Composites: Denier Variation

This example illustrates the effect that the variation in fiber denierin the first stratum of representative unitary stratified composites ofthe present invention has on the acquisition time and rewet of diapersincorporating the absorbent. Multiple-dose rewet tests were performed asdescribed above in Example 5 for a commercially available diaper anddiapers incorporating representative unitary stratified composites. Theresults are summarized in Tables 1 through 4 below. In Table 1, ControlDiaper A refers to a whole diaper commercially available fromKimberly-Clark. In Tables 2-4, Test Diapers 1-3 refer to theKimberly-Clark diaper incorporating representative unitary stratifiedcomposites having a first stratum composed of PET fibers having 1.5, 6,and 15 denier, respectively. The representative unitary stratifiedcomposites were produced by a wet laid method as described above inExample 1, and were formulated having a first stratum composed of 90%PET and 10% Celbond® and having a basis weight of about 22 g/m², and asecond stratum composed of 90% crosslinked cellulose fibers and 10%Celbond® and having a basis weight of about 70 g/m².

The results show that the diapers incorporating the absorbent compositeprovide significantly enhanced rewet performance and generally shorteracquisition times than the control diaper. The results also indicatethat increased fiber denier in the first stratum of the absorbentcomposite increases the absorbent composite's performancecharacteristics. The results are graphically illustrated in FIG. 8.

TABLE 1 Multiple-Dose Rewet Test: Control Diaper A SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 32.3 1st dose 33.87 20.7 20.8 0.1 2 34.8 1st dose 30.91 20.820.9 0.1 3 35.3 1st dose 26.47 20.8 20.9 0.1 4 34.9 1st dose 32.21 20.820.8 0 Average 30.87 Average 0.075 Std. Dev. 3.17 Std. Avg. 0.05 1 2nddose 52.90 30.7 34.0 3.3 2 2nd dose 43.69 30.7 31.7 1.0 3 2nd dose 45.9130.6 32.3 1.7 4 2nd dose 50.44 29.5 30.6 1.1 Average 48.24 Average 1.775Std. Dev. 4.19 Std. Dev. 1.08 1 3rd dose 69.03 40.4 74.3 33.9 2 3rd dose58.09 40.5 63.2 22.7 3 3rd dose 54.81 40.5 70.6 30.1 4 3rd dose 60.7240.5 86.0 25.5 Average 60.66 Average 28.05 Std. Dev. 6.08 Std. Dev. 4.95

TABLE 2 Multiple-Dose Rewet Test: Test Diaper 1 SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 34.1 1st dose 30.81 20.6 20.7 0.1 2 34.9 1st dose 29.18 20.420.5 0.1 3 34.6 1st dose 27.25 21.0 21.0 0 4 35.2 1st dose 27.63 20.720.7 0 Average 28.72 Average 0.05 Std. Dev. 1.63 Std. Avg. 0.06 1 2nddose 59.09 29.5 29.6 0.1 2 2nd dose 50.41 30.9 31.2 0.3 3 2nd dose 46.0630.6 32.3 1.7 4 2nd dose 47.16 30.7 30.8 0.1 Average 50.68 Average 0.55Std. Dev. 5.90 Std. Dev. 0.77 1 3rd dose 63.84 39.3 65.2 25.9 2 3rd dose58.97 40.5 58.2 17.7 3 3rd dose 50.56 39.8 60.6 20.8 4 3rd dose 78.2540.7 58.3 17.6 Average 62.91 Average 20.50 Std. Dev. 11.61 Std. Dev.3.89

TABLE 3 Multiple-Dose Rewet Test: Test Diaper 2 SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 34.8 1st dose 25.91 20.4 20.4 0.0 2 35.5 1st dose 25.87 20.620.7 0.1 3 34.1 1st dose 26.90 20.2 20.2 0 4 33.2 1st dose 22.53 20.820.9 0.1 Average 25.30 Average 0.05 Std. Dev. 1.91 Std. Avg. 0.06 1 2nddose 41.13 31.0 31.3 0.3 2 2nd dose 30.31 30.4 30.7 0.3 3 2nd dose 36.2530.2 31.9 1.7 4 2nd dose 35.69 30.5 40.3 9.8 Average 35.85 Average 3.03Std. Dev. 4.43 Std. Dev. 4.56 1 3rd dose 53.68 40.7 60.2 19.5 2 3rd dose46.07 40.7 59.6 18.9 3 3rd dose 57.28 39.8 63.3 23.5 4 3rd dose 56.0339.3 56.8 17.5 Average 53.27 Average 19.86 Std. Dev. 5.02 Std. Dev. 2.57

TABLE 4 Multiple-Dose Rewet Test: Test Diaper 3 SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 34.0 1st dose 25.03 20.6 20.7 0.1 2 34.7 1st dose 23.44 20.520.5 0 3 33.1 1st dose 23.75 20.4 20.5 0.1 4 35.0 1st dose 24.15 20.620.7 0.1 Average 24.09 Average 0.07 Std. Dev. 0.69 Std. Avg. 0.05 1 2nddose 36.16 30.6 40.8 10.2 2 2nd dose 31.16 30.7 37.2 6.5 3 2nd dose36.41 31.0 39.9 8.9 4 2nd dose 35.40 30.7 34.3 3.6 Average 34.8 Average7.30 Std. Dev. 2.45 Std. Dev. 2.90 1 3rd dose 47.38 40.9 65.0 24.1 2 3rddose 43.78 40.0 61.0 21 3 3rd dose 46.56 41.0 65.8 24.8 4 3rd dose 47.7840.0 61.4 21.4 Average 46.38 Average 22.83 Std. Dev. 1.80 Std. Dev. 1.91

Example 7 Evaluation of Acquisition Time and Rewet for a RepresentativeUnitary Stratified Composite: Binder Variation

This example illustrates the effect that the variation in binder inrepresentative unitary stratified composites of the present inventionhas on the acquisition time and rewet of diapers incorporating theabsorbent. Multiple-dose rewet tests were performed as described abovein Example 5 for a commercially available diaper and diapersincorporating representative unitary stratified composites. The resultsare summarized in Tables 5 and 6 below. The control diaper was the sameas for Example 6 above, and its performance summarized in Table 1. InTable 5, Test Diaper 4 refers to the Kimberly-Clark diaper incorporatinga representative unitary stratified composite having a first stratumcomposed of 90% PET fibers (15 denier, 0.5 inch length, crimped) and 10%cellulose acetate/triacetin treated fibers and having a basis weight ofabout 22 g/m², and having a second stratum composed of 90% crosslinkedcellulose fibers and 10% cellulose acetate/triacetin (with 10% triacetinadd-on) treated fibers and having a basis weight of about 70 g/m². InTable 6, Test Diaper 5 refers to the Kimberly-Clark diaper incorporatinga representative unitary stratified composite having a first stratumcomposed of 90% PET fibers (15 denier, 0.5 inch length, crimped) and 10%Celbond® and having a basis weight of about 22 g/m², and having a secondstratum composed of 90% crosslinked cellulose fibers and 10% Celbond®and having a basis weight of about 70 g/m². The representative unitarystratified composites were produced by a wet laid method as describedabove in Example 1.

The results show that the diapers incorporating the absorbent compositeprovide significantly enhanced rewet performance and generally shorteracquisition times than the control diaper. The results also indicatethat the absorbent composite that includes cellulose acetate/triacetintreated fibers as the binder provides enhanced performancecharacteristics. The results are graphically illustrated in FIG. 9.

TABLE 5 Multiple-Dose Rewet Test: Test Diaper 4 SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 36.0 1st dose 23.04 20.4 20.6 0.2 2 32.6 1st dose 25.68 20.320.6 0.3 3 32.8 1st dose 23.78 20.4 20.6 0.2 4 35.1 1st dose 23.40 20.720.8 0.1 Average 23.98 Average 0.20 Std. Dev. 1.18 Std. Avg. 0.08 1 2nddose 25.68 30.8 38.6 7.8 2 2nd dose 26.94 30.7 44.9 14.2 3 2nd dose34.16 30.8 46.3 15.5 4 2nd dose 22.38 29.5 39.6 10.1 Average 27.29Average 11.9 Std. Dev. 4.97 Std. Dev. 3.57 1 3rd dose 27.69 39.6 57.217.6 2 3rd dose 32.59 39.7 62.3 22.6 3 3rd dose 39.41 40.8 67.3 26.5 43rd dose 29.53 40.4 61.8 21.4 Average 32.31 Average 22.03 Std. Dev. 5.15Std. Dev. 3.67

TABLE 6 Multiple-Dose Rewet Test: Test Diaper 5 SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 37.2 1st dose 24.03 20.7 20.9 0.2 2 34.8 1st dose 24.81 20.921.1 0.2 3 33.2 1st dose 27.56 20.9 21.0 0.1 4 34.5 1st dose 27.10 20.921.0 0.1 Average 25.88 Average 0.15 Std. Dev. 1.72 Std. Avg. 0.06 1 2nddose 25.46 30.8 34.3 3.5 2 2nd dose 32.94 30.7 43.2 12.5 3 2nd dose33.22 30.7 44.3 13.6 4 2nd dose 35.81 30.9 40.8 9.9 Average 31.86Average 9.88 Std. Dev. 4.46 Std. Dev. 4.52 1 3rd dose 33.47 40.5 56.6 162 3rd dose 38.75 40.7 61.3 20.6 3 3rd dose 45.62 40.9 65.0 24.1 4 3rddose 45.37 40.0 61.5 21.5 Average 40.80 Average 20.56 Std. Dev. 5.83Std. Dev. 3.38

Example 8 Evaluation of Acquisition Time and Rewet for a RepresentativeUnitary Stratified Composite: Densified and Undensified

This example illustrates the effect that densification of arepresentative unitary stratified composite of the present invention hason the acquisition time and rewet of diapers incorporating the absorbentcomposite. Multiple-dose rewet tests were performed as described abovein Example 5 for a commercially available diaper and diapersincorporating densifled and undensified representative unitarystratified composites. The results are summarized in Tables 7-9 below.In Table 7, Control Diaper B refers to a whole diaper commerciallyavailable from Proctor and Gamble. In Tables 8 and 9, Test Diapers 6 and7 refer to the Proctor and Gamble diaper incorporating representativeundensified and densified unitary stratified composites, respectively.The representative unitary stratified composites were produced by a foammethod as generally described above in Example 4, and were formulatedhaving a first stratum composed of 80% PET fibers (15 denier, 0.5 inchlength, crimped) and 20% Celbond® and having a basis weight of about 40g/m², and a second stratum composed of 80% crosslinked cellulose fibersand 20% Celbond® and having a basis weight of about 110 g/m². Thedensified unitary stratified composite was prepared by cold calenderingdensification to 0.064 g/cm³. The undensified absorbent composite had adensity of about 0.030 g/cm³.

The results show that the diapers incorporating the absorbent compositeprovide significantly enhanced rewet performance and generally shorteracquisition times than the control diaper. The results also indicatethat undensified unitary stratified composite increases the absorbentcomposite's performance characteristics. The results are graphicallyillustrated in FIG. 10.

TABLE 7 Multiple-Dose Rewet Test: Control Diaper B SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 48.0 1st dose 20 20.86 20.95 0.09 2 48.0 1st dose 21 20.11 20.210.1 3 48.0 1st dose 21 20.32 20.42 0.1 Average 20 Average 0.10 Std. Dev.0 Std. Avg. 0.01 2nd dose 23 30.47 34.76 4.29 2nd dose 25 30.52 36.015.49 2nd dose 25 30.94 33.48 2.54 Average 24 Average 4.11 Std. Dev. 1Std. Dev. 1.48 3rd dose 44 40.84 61.02 20.18 3rd dose 36 39.24 57.4018.16 3rd dose 37 39.27 62.83 23.56 Average 39 Average 20.63 Std. Dev. 4Std. Dev. 2.73

TABLE 8 Multiple-Dose Rewet Test: Test Diaper 6 SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 45.6 1st dose 14 20.66 21.17 0.51 2 45.6 1st dose 15 19.18 19.650.47 3 45.6 1st dose 14 19.14 19.72 0.58 Average 14 Average 0.52 Std.Dev. 0 Std. Avg. 0.06 2nd dose 17 30.97 33.60 2.63 2nd dose 15 29.2730.54 1.27 2nd dose 18 29.29 32.31 3.02 Average 17 Average 2.31 Std.Dev. 1 Std. Dev. 0.92 3rd dose 21 39.43 60.28 20.85 3rd dose 19 39.2852.97 13.69 3rd dose 18 39.82 64.31 24.49 Average 19 Average 19.68 Std.Dev. 2 Std. Dev. 5.49

TABLE 9 Multiple-Dose Rewet Test: Test Diaper 7 SAMPLE AcquisitionSAMPLE WEIGHT Time BLOTTER WT. (grams) NO. (grams) (seconds) dry wet wet− dry 1 46.0 1st dose 19 19.04 19.18 0.14 2 46.0 1st dose 21 20.39 20.760.37 3 46.0 1st dose 22 20.54 20.91 0.37 Average 21 Average 0.29 Std.Dev. 1 Std. Avg. 0.13 2nd dose 21 29.19 31.92 2.73 2nd dose 18 30.6239.36 8.74 2nd dose 23 29.23 33.15 3.92 Average 21 Average 5.13 Std.Dev. 2 Std. Dev. 3.18 3rd dose 28 39.45 58.76 19.31 3rd dose 22 39.6460.36 20.72 3rd dose 31 39.80 64.73 24.93 Average 27 Average 21.65 Std.Dev. 5 Std. Dev. 2.92

While the preferred embodiment of the invention has been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An absorbent article,comprising: (a) a liquid pervious topsheet; (b) a wetlaid absorbentcomposite, comprising a first stratum, a second stratum, and atransition zone intermediate and coextensive with the first stratum andthe second stratum; the first stratum comprising hydrophobic fibers anda binder; the second stratum comprising a binder and fibers selectedfrom the group consisting of hydrophilic fibers, hydrophobic fibers, andmixtures thereof; and the transition zone comprising fibers from thefirst stratum and the second stratum commingled substantially uniformlyacross the composite's width and along the composite's length; (c) astorage stratum comprising an absorbent fibrous material; (d) anintermediate stratum interposed between the absorbent composite and thestorage stratum; and (e) a liquid impervious backsheet.
 2. The absorbentarticle of claim 1, wherein at least one of the first or the secondstratum comprises synthetic fibers.
 3. The absorbent article of claim 1,wherein the second stratum further comprises crosslinked cellulosicfibers.
 4. The absorbent article of claim 1, wherein at least one of thebinders comprises a bicomponent fiber or a wet strength agent.
 5. Theabsorbent article of claim 1, wherein the article is an adultincontinence product.
 6. The absorbent article of claim 1, wherein theintermediate stratum comprises a liquid pervious tissue.
 7. Theabsorbent article of claim 1, wherein the intermediate stratum comprisesa distribution stratum.
 8. The absorbent article of claim 7, wherein thedistribution stratum comprises hydrophilic fibers and a binder.
 9. Theabsorbent article of claim 8, wherein at least one of the second stratumor the distribution stratum comprises crosslinked cellulosic fibers. 10.The absorbent article of claim 8, wherein at least one of the secondstratum or the distribution stratum comprises crosslinked eucalyptusfibers.
 11. An absorbent article, comprising: (a) a liquid pervioustopsheet; (b) a wetlaid absorbent composite, comprising a first stratum,a second stratum, and a transition zone intermediate and coextensivewith the first stratum and the second stratum; the first stratumcomprising first fibers and a binder; the second stratum comprisingsecond fibers and a binder; and the transition zone comprising fibersfrom the first stratum and the second stratum commingled substantiallyuniformly across the composite's width and along the composite's length;(c) a storage stratum comprising an absorbent fibrous material; (d) anintermediate stratum interposed between the absorbent composite and thestorage stratum; and (e) a liquid impervious backsheet.
 12. Theabsorbent article of claim 11, wherein the first fibers comprisesynthetic fibers.
 13. The absorbent article of claim 11, wherein thesecond fibers comprise crosslinked cellulosic fibers.
 14. The absorbentarticle of claim 11, wherein at least one of the binders comprises abicomponent fiber or a wet strength agent.
 15. The absorbent article ofclaim 11, wherein the article is an adult incontinence product.
 16. Theabsorbent article of claim 11, wherein the intermediate stratumcomprises a liquid pervious tissue.
 17. The absorbent article of claim11, wherein the intermediate stratum comprises a distribution stratum.18. The absorbent article of claim 17, wherein the distribution stratumcomprises hydrophilic fibers and a binder.
 19. The absorbent article ofclaim 18, wherein the hydrophilic fibers comprise crosslinked cellulosicfibers.
 20. The absorbent article of claim 18, wherein the hydrophilicfibers comprise crosslinked eucalyptus fibers.
 21. An absorbent article,comprising: (a) a liquid pervious topsheet; (b) a wetlaid absorbentcomposite, comprising a first stratum, a second stratum, and atransition zone intermediate and coextensive with the first stratum andthe second stratum; the first stratum comprising synthetic fibers and abinder; the second stratum comprising crosslinked cellulosic fibers anda binder; and the transition zone comprising fibers from the firststratum and the second stratum commingled substantially uniformly acrossthe composite's width and along the composite's length; (c) a storagestratum comprising an absorbent fibrous material; (d) an intermediatestratum interposed between the absorbent composite and the storagestratum; and (e) a liquid impervious backsheet.
 22. The absorbentarticle of claim 21, wherein at least one of the binders comprises abicomponent fiber or a wet strength agent.
 23. The absorbent article ofclaim 21, wherein the article is an adult incontinence product.
 24. Theabsorbent article of claim 21, wherein the intermediate stratumcomprises a liquid pervious tissue.
 25. The absorbent article of claim21, wherein the intermediate stratum comprises a distribution stratum.26. The absorbent article of claim 25, wherein the distribution stratumcomprises hydrophilic fibers and a binder.
 27. The absorbent article ofclaim 26, wherein the hydrophilic fibers comprise crosslinked cellulosicfibers.
 28. The absorbent article of claim 26, wherein the hydrophilicfibers comprise crosslinked eucalyptus fibers.